JPH01183374A - Slip detector for motor driven driver - Google Patents

Abstract

PURPOSE:To make it possible to surely detect slip of the captioned motor driven driver on tightening by providing a means for judging bit slip as present, in the case that the rotational number of the motor driven driver after starting of the tightening exceeds a predetermined value. CONSTITUTION:As a screw reaches a bearing surface, a tightening command is input in a motor controller 6 so as to increase a supply voltage to a motor 7 and the tightening of the screw is thus started with the use of a bit 8. In this case, an increased current value is detected by a current detector 10 of a tightening start detector 1 and the result is input in a judging device 3. Next, the rotating number of the motor 7 after starting of the tightening is detected by a rotation detector 2 and the detected signal is input in the judging device 3. The rotational number input to the judging device 3 is compared with a predetermined value and if the rotational number exceeds the predetermined value, the slip of the bit 8 is judged as present, then the result being transmitted to a display 4 for displaying it to the outside.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a slippage detection device for an electric screwdriver.

<Prior Art> Electric screwdrivers have been widely used for tightening screws in precision instruments such as watches. When using an electric screwdriver, it is common to tighten the screw by increasing the voltage supplied to the electric screwdriver's motor when screw tightening is complete, but when retightening, the tightening torque increases, which can cause the electric screwdriver to slip. Sometimes. This slippage can occur when the electric screwdriver's cutting edge and the screw head do not fit together, or when the electric screwdriver's pushing force is weak, but in any case, if slippage occurs during retightening, the screw tightening strength will be extremely low. There is a problem in that the work is finished while the product is still weak, resulting in defective products.

In the case of manual work, the worker can detect the occurrence of slippage, but in recent years, electric screwdrivers are often operated by robots, and when robots are used, there is no means to detect the occurrence of slippage, and tightening is incomplete. It will be sent to the next process as it is.

<Summary of the Invention> The present invention has been made to improve the above-mentioned conventional problems, and includes means for detecting the start of retightening of an electric screwdriver, and means for detecting the rotation speed of the electric screwdriver after the start of retightening. The basic feature is that the electric screwdriver has a means for comparing the detected rotational speed of the electric screwdriver with a predetermined value and determining that there is slippage when the rotational speed is greater than or equal to the predetermined value.

<Operation> When the electric screwdriver starts retightening, this is detected by the detection means, and the rotation speed of the electric screwdriver after the retightening is started is detected by the detection means. If the rotation speed is a predetermined value, it is determined that there is slippage.

<Example> An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, the electric screwdriver is powered by a power source 5. Motor control device6. It consists of a motor 7 and a bit 8. A retightening command is input to the motor control bag M6 manually by the operator or from another control device, etc., and the motor control bag W16 responds to this command signal by increasing the voltage supplied to the key tough to increase the rotational torque of the motor 7. Increase and retighten.

The slippage detection device according to the present invention includes a retightening start detection device 1. The retightening start detection device 1 includes a current detector 10, which detects the current flowing through the motor 7 via the motor control device 6, and detects the start of retightening based on a change in this current value. That is, when the voltage supplied to the motor 7 is increased due to the start of retightening, the current value increases, so it is possible to detect the start of retightening by detecting this increase in current. The retightening start detection output of the retightening start detection device 1 is sent to the determination device 3. On the other hand, a rotation detector R2 for detecting the rotation speed of the motor 7 is provided. As this rotation detection device 2, a rotation detector using optical detection or the like may be used, and in this embodiment, a rotation signal of 6 pulses is output every time the motor 7 rotates once. The output of this rotation detection device 2 is sent to a determination device 3.

After inputting the retightening start signal from the retightening start detection device 1, the determination device 3 detects the subsequent rotation speed of the motor 7 using the rotation detection device 2, and compares it with a predetermined rotation speed. When retightening, the motor 7 hardly rotates.
For example, it can be determined that slippage has occurred if the rotation is more than half a turn. In this embodiment, the determination device a3 is set to half a rotation as a predetermined value, and if the rotation detection pulses from the one rotation detection device 2 are three or more pulses, it is determined that slipping has occurred.

The determination output from the determination device 3 is output to the display device 4,
Displayed 0 For example, the system is configured to display the occurrence of slippage using a warning light or the like.

- Next, the operation of the above configuration will be explained based on FIG. When the electric screwdriver starts, as shown in Figure 2, an overcurrent flows through the motor 7, but this current immediately drops and reaches a steady state (periods a, b), which starts tightening the screws and gradually tightens the screws. As the torque increases, the current value also gradually increases (period c). When the s screw reaches the seat surface, the rotation of the motor 7 stops. Here, when a retightening command is input to the motor control device 16, the motor control device 16 increases the supply voltage and causes the motor 7 to perform retightening. At this time, one period d
As shown in , the current value increases. The retightening start detection bag N1 detects this increase in current value using the current detector 10, and detects the start of retightening. This detection result is determined by the determination device 3.
sent to.

The current flowing through the motor 7 gradually increases as the retightening is performed, and during period e), when the retightening is completed.

In response to an operation by the operator or a signal from the control device, the remote control device 6 stops supplying power and finishes screw tightening (period f).During periods e and f, the determination device 3 determines whether the rotation detecting device 2 detects the motor. 7 rotation speed signal is input and compared with a predetermined rotation speed. In this embodiment, as described above, if there is a rotation beyond half a rotation, it is determined that the bit 8 is slipping. This determination result is sent to the display bag R4 and displayed externally.

Through the above-described operations, slippage of the electric screwdriver can be detected reliably, and defects in tightening can be dealt with. Note 1
The determination result of the determination device 3 may be configured to be fed back to, for example, a robot operating an electric screwdriver.

<Effect of the invention> .

As explained above, the electric screwdriver slippage detection device of the present invention includes a means for detecting the start of retightening of the electric screwdriver, a means for detecting the rotation speed of the electric screwdriver after the start of retightening, and a means for detecting the rotation speed of the electric screwdriver after the start of retightening. Since it has means for comparing the number of rotations with a predetermined value and determining that there is slippage when the number of rotations is equal to or higher than the predetermined value, it is possible to reliably detect slippage of the electric screwdriver during retightening.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between motor current and time to explain the operation. 1: Retightening start detection device, 2: Rotation detection device, 3: Determination device, 4: Display device, 5: Power supply, 6: Motor control device, 7: Motor, 8: Bit, 10: Current detector. Patent applicant Hayashi Watch Industry Co., Ltd. Agent Patent attorney Takashi M and 1 other person Figure 1 Figure 2 ab c def

Claims (1)

[Scope of Claims] Means for detecting the start of retightening of the electric screwdriver, means for detecting the rotation speed of the electric screwdriver after the start of retightening, and comparing the detected rotation speed of the electric screwdriver with a predetermined value,
A slip detection device for an electric screwdriver, comprising: means for determining that slippage occurs when the rotational speed is equal to or higher than a predetermined value.